<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
    .f{
        width: 350px;
        height: 500px;
        background: url(./images/file1.jpg) no-repeat;
        position: relative;
        left: 0px;
        top: 0px;
        
    }

    #triangle-bottomleft {
            width: 0;
            height: 0;
            border-bottom: 150px solid white;
            border-right: 300px solid transparent;
            position: relative;
            left: 0px;
            top: 300px;
        }

    .s{
        width: 0;
            height: 0;
            border-bottom: 150px solid transparent;
            border-left: 300px solid transparent;
            position: relative;
            left: 500px;
            top:135px;
            transition: all 2s linear 0s;
    }   

    .f:hover .s{
        border-bottom: 150px solid greenyellow;
            left: 50px;
            top: 134px;

    }
    </style>
</head>
<body>
    <div class="f">
        <div id="triangle-bottomleft"></div>
        <div class="s" id="triangle-bottomright"></div>
    </div>
    
</body>
</html>